Art of electrical-wave transmission.



No. 789,087. PATENTBDiMAY 2, 1905. 0Q D. EHRET.

ART OF ELECTRICAL WAVE TRANSMISSION.

APPLICATION FILED 1030.3, 1901.

2 SHBBTSSHEET 1.

jnnnnmmz 1 WWW .z mum I I l Inventor No. 789.087. PATENTED MAY 2, 1905.

C. D. BHR'BT.

ART 0 ELECTRICAL WAVE TRANSMISSION. APPLIOATIQN FILED D110. 3, 1901.

2 SHEETS-SHEET 2.

Inventar 1 STATES Patented May 2, 190 5.

PATENT OFFICE.

ART OF ELECTRICAL-WAVE TRANSMISSION.

SPECIFICATION forming part of Letters Patent No. 789,087, dated May 2, 1905.

Application filed December 3, 1901. Serial No. 84,512.

To 0066 whom, it may concern.-

Be it-known that I, CORNELIUS D. EHRET, a citizen of the United States, residing at Washington, District of Columbia, have invented certain new and useful Improvements in the Artof Electrical- Wave Transmission, of which the following is a specification.

My invention comprises a method of transmitting and amplifying electric waves used in signaling, particularly telephony. Its essential feature consists in adding energy to the signal-waves after they have traversed a great portion of a circuit and have become attenuated.

In one of its aspects the invention comprises a telephone or telegraph repeater.

It comprises, further, method of impressing upon the signal circuit electric waves and method of modifying such waves by and in accordance with sound-waves or in accordance with any code.

It comprises, further, a method of transmitting simultaneously over the-same circuit two or more independent telegraphic or telephonic messages with means for selecting to the proper instrument the telephonic or telegraphic message intended therefor. tegether with means for amplifying each of the messages so simultaneously transmitted during its transit.

It comprises, further, a method of impressing upon a circuit electric waves, preventing their distortion and attenuation by static means, and. further, in reinforcing and amplifying such methods during transit.

So far as I am aware there exists at present no commercially successful telephone relay or repeater. Instruments constructed on the principle of receiving the weakened telephonemessage in a magnetic receiver and causing such receiver to actuate a microphonic contact in a new circuit are unsuccessful. The distance over which telephone-messages are capable of transmission with instruments now in use is limited to one thousand or fifteen hundred miles. This is due to the detrimental effects of distributed capacity, resistance, and leakage of the circuit, which operate to attenuate and distort the current-waves representing the message.

By the system herein disclosed it is proposed to extend the distance over which commercial telephony can be practiced by impressing upon the circuit a high-frequency alternating current, modifying the amplitude of the waves of such current by and in accordance with sound-waves, and amplifying the alternating-current waves atsuch points in the circuit where they will have become seriously attenuated. This amplification or boosting effect is accomplished by a piece of apparatus well known in alternating-current power-work as the induction or asynchronous generator. In construction the inductiongenerator is precisely the same as the induction or asynchronous motor. The induction-motor when driven above synchronous speed becomes a generator and adds energy to the circuit to which it is connected, provided there at all times exists upon such circuit an alternating current to always supply the primary winding with current.

The frequency of the added energy is precisely that of the energy flowing through the primary winding and establishing its initial field. I

In my system the alternating current, which has been modified as to the amplitudes of the current waves by the signal transmitting means, is led through the primary winding of the induction-generator, and so acts as a frequency-setter for the generator, and the mechanical energy supplied to the rotating member of the generator appears in the primary winding as boosted or added energy. In consequence the signal-waves instead of dying out and becoming valueless are reinforced to the end that communication can be carried on over longer distances than heretofore possible.

Reference will now be had to the drawings for a more detailed description of the system.

Figures 1 and 2 are diagrammatic representations of impressed and modified alternatingcurrent waves. Fig. 3isadiagram showinga simple circuit in which are inserted at intervals induction-generators. Fig. 4 is a modification of the system,showing metallic circuit and terminal local circuits along with the inductiongenerators. Figs. 5 and 6 are diagrammatic route.

views of means for generating the alternatingeurrent waves which are to be impressed upon the circuit. Fig. 7 is a diagrammatic view of one means of modifying the impressed waves in accordance with speech. Fig. 8 is a diagrammatic view of the magnetic wave form and the resulting secondary wave form obtained in the generating apparatus shown in Fig. 6. Fig. 9 isa graphic representation of the attenuation of the message in transit and the result of boosting at certain intervals.

Fig. 10 shows another modification of means for modifying the impressed alternating-current waves by and in accordance with soundwaves. Fig. 11 shows a metallic circuit upon which is impressed at the middle points of the circuit the alternating current waves, which may be termed a central energy system and which also shows the induction-generators, one in each side of the circuit at each reinforcingstation. Fig. 12 shows a metallic circuit with a modified means of impressing the alternating energy upon it at the middle thereof along with modified means for varying the alternating energy in accordance with speech. Fig. 13 is a metallic circuit for conveying at the same time two telephonic messages and reinforcing them 011 Fig. 14 shows the generating-station at the middle of ametalliccircuitforimpressing alternating current upon the same along with inductance-coils distributed at certain intervals and also the reinforcing inductiongenerators.

In Fig. 1 is represented a series of high-frequency alternating-current waves. By high frequency is meant such frequency as is high in comparison with the more essential frequencies in sound-waves occurring in human speech. For example, such frequency may be in the neighborhood of fifteen hundred per second or of course much higher. If a current of such frequency be passing over a circuit and if the amplitudes of the waves be modified by means of telephonic transmitting devices, the succeeding waves will be of different amplitudes, as shown in Fig. 2, and a curve tangent to the tops of the waves will graphically represent the sound-waves uttered against the telephone-transmitter. However, all frequencies of the voice in excess of the frequency of the impressed current will not modify the impressed current-waves, but will exist upon the circuit independently and will practically go to. waste. If it is desired to improve the timbre of the received message, the frequency of the impressed waves should be increased above fifteen hundred to whatever limit desirable, for the reason that it is the higher frequencies in the speech which go, to make up its quality. However, the higher frequencies can be neglected and articulate speech obtained, by preserving the lower harmonies only.

In Fig. 3, A is a dynamic generator of alternating current of high frequency one terminal of which connects to earth a and the other to the telephonic transmitter T. The current impressed upon the line is modified by and in accordance with sound-waves by said transmitter T and passes over the circuit to the receiver R and to earth a. The receiver R is of a type well known in high-frequency workingsuch, for example, as the two-coil receiver, in which a stationary coil and a coil carrying or operating upon a diaphragm are connected in series or parallel with each other. At two points in the circuit are shown the induction-generato-rsl, whose primary windings f are in the line and whose rotors or secondaries are shown at a" and. comprise, as is well known, a series of short-circuited conductors, there being no electrical connection from said rotor to. any external circuit. Supposing the generator A to. be at a transmitting-station and the current-waves to have been modified in accordance with speech by talking into the transmitter T, a series of waves exists upon the line, as represented in Fig. 2. However, these waves become distorted and attenuated, due tothe evil effects of distributed capacity, resistance, and leakage existing in the circuit. At a considerable distance to the right of the transmitting-station, where said Waves have become seriously reduced in their energy, they are reinforced in the Well-known manner by the induction-generator I by the relative rotation of the rotor and stator at a speed in excess of synchronous speed for the frequency of the impressed-current waves. The waves then pass on and when again attenuated are again reinforced by the second inductiongenerator I and are eventually received at R with suflieient amplitude to strongly reproduce sound-waves or speech.

Reference is to be had to Fig. 9, in, which the ordinates represent amplitudes of the waves and the abscissae platted along thev axis 0 z distances from the transmitting-station. The attenuation follows a logarithmic law and is graphically represented by the curve 1 n and in this figure is shown to reach the reeeiving-station with an amplitude .2 n, provided there has been no boosting. However, by the use of two induction-generators, as shown in Fig. 3, the current is boosted at one-third and two-thirds distance from the transmitter, so that when received the amplitude instead of being z n is 2 m. It is to be understood, however, that more inductiongenerators can be inserted in the line and, furthermore, that at each one a greater am plification may be brought about than is indicated in Fig. 9.

Fig. 4 shows a metallic circuit with asoureeof alternating currents of high frequency at A, which are fed to the, primary of the transformer 7), in which is located a telephonic transmitter T. The modified waves at high pressure pass from the secondary to line and en route are amplified by the induction-generators I, as in the case shownin Fig. 3.

There are at each relay-station two induction-generators I, as shown, and which may be mounted on the same shaft and driven by the same prime mover. The receivers R arein the main line. As shown, the energy is all supplied from one end of the circuit; but a second generator A (shown in dotted lines at the right) may also be used if run synchronously with the generator at the left hand of the circuit.

In place of the generator A there may be used, as shown in Fig. 5, a direct-current generator Gr, supplying current through W, a VVehnelt interrupter, with the resistance a. Tapped off from the resistance a is the primary circuit of the transformer b, which includes the telephonic transmitter T.

In Fig. 6, G is a direct-current generator, supplying current to the ring of resistance material. The brush 2' is connected at opposite ends of a diameter, and brush j is connected to opposite ends of a second diameter at right angles to the one first named. Brush 1' is also connected to one terminal of the primary of the transformer b. The other terminal of the primary is connected to the telephone-transmitter T and thence to the trailer cl, which is driven by belt it, running over pulley As the trailer revolves at high speed the primary 6 receives a uniformly rising and falling difference of potential at its terminals, and the current resulting therefrom produces a magnetic effect in the core of the transformer, (graphically represented in the upper portion of Fig. 8.) As a result the secondary waves will be flat-topped, as shown in the lower portion, though in practice they will be rounded at their tops. It is desirable, so far as possible, to have broad-topped waves, to the end that the members in the receiver are more uniformly under stress.

In Fig. 7 A represents a generator of alternating currents of a frequency higher than the more essential frequencies of speech. Z) is a transformer in whose secondary circuit are included the battery B and the telephonetransmitter T. By speaking into the transmitter T the amplitudes of the current-waves impressed upon the line-circuit are varied in accordance with speech, as represented in Fig. 2.

In Fig. 10 is shown a core 0, upon which at the upper end is a coil fed from the generator A, furnishing alternating currents of high frequencythat is, of frequency higher than the more essential voice frequencies. The middle coil is connected to line, and the circuit of the lower coil embraces the battery B and telephonic transmitter T. The latter when spoken into causes, in view of the relation of the windings, a variation in the inductance of the remaining coils,such variation corresponding to speeclrwaves, the result being an impression upon the line of high-frequency alternating-current waves whose amplitudes are varied by and in accordance with sound or speech waves.

Fig. 11 shows a metallic circuit with two generators A at the middle point. It represents, in effect, a central energy system and permits talking from either end of the circuit with equal facility. The two generators A must supply currents to the line in synchronism and to that end, if the generators A be similar, should have their rotating members mounted upon the same shaft. Speaking into the telephonic transmitter T at either end of the circuit varies the amplitudes of the alternating-current waves passing over the same. These as they become attenuated are amplified by the induction-generators I, of which there are two at each station and preferably have their rotating members mounted upon the same shaft, as stated in connection with Fig. 4.

Fig. 12 shows a metallic circuit with the energy supplied at the middle point from the generator A through the two transformers I) Z). Synchronism is by this means obtained with certainty, and care should be taken in connecting the transformers to the circuit that they aid each other. As in Fig. 11, two inductiongenerators are shown at each relay-station, and the terminal stations comprise the receivers R, the transformers t, and telephonic transmitters T.

In Fig. 13 there are shown the left-hand end and the central energy-stations of a circuit adapted for multiple telephony. Upon the line through transformers b are impressed alternating currents of different frequencies, one by generator A and the other by generator A. In circuit with the generator A is the condenser C and inductance L. The product of the capacity of C and inductanceof L is such as to make the primary circuit, including A, resonant to the frequency generated by A. In connection with the generator A is the condenser C and the inductance L, the purpose of C and L being the same as stated in connection with C and L in the circuit of A. In the relaying-station at each side of the line are shown two induction-generators I and I. In series with I is the inductance L and capacity C, comprising altogether a resonant circuit, which will select out the alternating current impressed upon the line by the generator A and reinforce it. In circuit with I is the condenser C and inductance L', which, with 1, form a resonant circuit adapted to select out the alternating current supplied by generator A. The

rotors of the two induction generators I are oined on the same shaft, while the rotors of the two induction-generators l are upon another shaft, or, in fact, all may be upon the same shaft and driven by the same prime mover, provided the correctvnum-ber of poles' is provided. It is seen, therefore, that each current is'selected out to its proper reinforc- It :is to be noted that inasmuch as L 0 form aresonant circuit the potentialat the terminals R is greater than that across the circuit at the receiving-station. In the other telephone instrument there is showncondenser O in series with inductance If, primary-of the transformerl), and the receiver B3. In the secondary-of transformer- 6 is a simple microphone T. Theelectricalconstants of thistelephoneset :is such asto make it resonant to the current impressed upon the'circuit by the-generator A, and in consequence a-message intended forsuchreceiver will be properly selected-out from anyother telephonicmessages which may be existing.uponthe circuit atthe same time.

In Fig. 1 1 is shown a middle portionsof a metallic circuit in which A is a generator of alternatingcurrent of low frequency supplying current through the transformer b to the circuit C b b L. The constants of the lastnamed circuit are such that when vibrating freely it hasa periodicity of {fifteen hundred per-second-or more. from the transformer I) in conjunction with thealternator A and when fully charged discharges across the spark-gap s and vibrates freely at the above-mentioned rate. There are impressed, therefore, upon the line the required high-frequency alternating waves. However, the means for impressing a highfrequency current on the line+circuit, as shown in Fig. 12 and others, may be substituted. At uniform distances along the main circuit are inductance-coils p, which aid in reducing distortion and attenuation of the transmitted waves of single frequencies. Induction-generators I are shown as replacing certain inductance-coils ofthe series, and at-these points the waves are amplified in the same manner as described in connection with the-other figures. It is to be noted that the inductance-of the primary of these induction-generators I when in operation may be such as to be exactly equivalent to'the coil replaced by such generator.

In the sec- This circuit is charged The induction-generators now used for the low frequencies of from twenty-five to one hundred and thirty-three periods per second in lighting and powercircuits are not perfectly suitable for the high-frequency service .required inconnection with this system. The presenceof great masses of iron in the magnetic circuits is objectionable in that the hysteresis effects cause odd harmonics of the impressedalternating-current waves and interfere tosomeextent with the operation of the system. The generators used in the systems describediherein should therefore be specially designed with little or no iron in the magnetic circuits,.and the rotors should be of a construction preferably disk-shaped to permit of high rotary velocities.

.It-has been proposed to use in the ordinary telephone systemthat is, where the current on the line isian extremely complex one having all the different frequencies found in -speechan induction-generator for the purpose-of reinforcing the complex current during transmission. Such system is unsuccessful becausethe different frequencies of the complex current would be reinforced to different extents, thus amplifying greatly the low frequencies,-and the high frequencies to a far less extent, with the result that-the reproduction of speech would be impossible. In contradistiction to this disadvantage the system'herein described reinforces all voice frequencies equally up to and including the frequency of the current normally existing or-impressed upon the line. The result is that the timbre by this system remains or conforms more nearly to the natural than in the proposed system, where the reinforcement is not uniform.

In the transmission of currents over circuits whoselengthzis so great that the wave phenomena are developed occur distortion and attenuation. evils .bea .minimum, the ohmic resistance of the circuit should be as small aspossible, while the distributed inductance should be as large aspossible. For minimum distortion the leakage should be relatively large and the capacity per unit length should be as small as possible. As to the attenuation, it is aminimum when the leakage is least and the capacity greatest that is, the best conditions for distortion and attenuation are opposed when con- 'sidering the leakage and capacity per unit length.

In order that each of these.

and therefore capable of being reinforced by an induction-generator, and at such points as desirable. At the same time that such leakage is introduced the danger of too great attenuation is overcome by the presence of the above mentioned boosters. To carry this principle into operation, I provide, as shown in either Fig. 11 or Fig. 14, leak-circuits 7a, which are distributed over the entire circuit at preferably regular intervals, such intervals being some small fraction of the wave length of the transmitted current. In Fig. 11 such leaks are applied to a circuit in which no inductance-coils are present, whereas in Fig. 14 such leaks Ir are provided at the intervals between the ingluctance-coilsp, described in connection with such figure above. It is to be understood also that leak-circuits can be applied to all of the arrangements of circuits herein shown.

WVhile the leaks may be applied at regular intervals at the rate of a plurality within a wave length, it is to be understood they may be applied at irregular intervals greater or less than a wave length.

The leak-circuits k, extending from the circuit-wires to earth or joining the two conductors of a circuit, may include high resistances, inductances, or condensers or suitable combinations of the same. However, either resistance or inductance leaks are preferred.

By the herein-described system, in which a current of practically constant frequency is impressed upon the line, distortion is reduced by the employment of leakage and may be further reduced by the employment of inductance. The attenuation resulting from leakage and other causes is compensated for or more than compensated for by the inductiongenerator, which reinforces the simple current of practially constant frequency, the Waves of different amplitudes being reinforced proportionately to their amplitudes, thus preserving the form of the transmitted energy as originally modified and impressed upon the line. Inductance is not essential to the herein-described system, since distortion can be reduced by leakage and the attenuation then overcome by reinforcement. The greater the amount of leakage the less inductance necessary for keeping the distortion within practical limits. However, it is of advantage to employ inductance and when employed may be obtained by lumped inductances connected in series in the circuit at regular intervals or may be obtained by any other suitable means or distribution, as suggested by Heaviside.-

- It is to be understood that for any of the telephonetransmitters or transmitting devices herein shown and described may be substituted any of the well-known telegraphic transmitters or transmitting devices. Thus a simple telegraphic key, perforated tape transmitter, or, in fact, any of the transmitters in the art of telegraphy may be employed to control the alternating, fluctuating, or other current impressed upon the circuit. Similarly, the telephone-receivers herein shown may be replaced by any suitable telegraphreceivers. In telegraphy the frequency of the fluctuating or alternating current need be a moderate one onlyas for example, ordinary commercial frequencies of from twentyfive to one hundred and thirty-three cycles per secondor higher, if desired.

I do not wish to be limited to the precise arrangement of circuits or means for generating the alternating currents or for modifying them, as any equivalent devices of those shown may be used and are comprehended in the scope of the appended claims. In fact, either generators of broad top waves or the more usual generators of sine-waves, as A, may be employed.

Claims to the apparatus herein disclosed are made in my divisional application, Serial No. 111,241, filed June 12, 1902.

What I claim as new, and desire to secure by Letters Patent, is

1. The method of transmitting signals which consists in impressing an alternating or fluctuating current upon a circuit, modifying said current to form a signal, permitting leakage of said current, reinforcing said current, and passing the modified current through a receiver to reproduce the signal.

2. The method of transmitting signals which consists in impressing an alternating or flue tuating current upon a circuit, modifying said current in accordance with the signal to be sent, reducing the distortion of the currentwaves by the effects of inductance and leakage, reinforcing said current to reduce the attenuation thereof, and passing the modified current through a receiver to reproduce the signal.

3. The method of transmitting signals which consists in impressing electrical energy upon a circuit, modifying said energy in accordance with the signal to be sent, reducing the distortion of the energy-Waves by the effects of inductance and leakage, reinforcing said energy to reduce the attenuation thereof, and passing the modified energy through a receiver to reproduce the signal.

4. The method of reinforcing electric signals, which consists in passing the alternating or fluctuating current modified in accordance with the signal through the primary of an induction-generator, and rotating the secondary above synchronism.

5. The method of transmitting speech,which consists in impressing upon an electric circuit a high-frequency alternating current, modifying said current by and in accordance with sound-waves, permitting leakage of said current, boosting said modified current, and passing it through a'receiver to reproduce speech.

6. The method of transmitting signals which consists in impressing electric energy upon a circuit; modifying said energy to form a signal; dissipating a portion of said energy by leakage; reinforcing said energy; and passing the reinforced energy through a receiver to reproduce the signal.

7 The method of transmitting messages,

message to be transmitted, dissipating a por tion of the energy of said'curren't by numerous leaks along the circuit, reinforcing said energy by an induction-generator, and passing'the arriving energy through a receiver to reproduce a message.

9. The method of transmitting speech,which consists in impressing upon a circuit an alternating or fluctuating current having a frequency higher than the more essential voice frequencies, modifying the energy of said current by and in accordance with speech, reduc' ing distortion of said current by the effects of inductance and leakage, boosting or reinforcing the transmitted energy as modified, and passing the arriving energy through a receiver to reproduce speech.

10. The method of transmittingintelligence, which consists in impressing upon a circuit an alternating current of afrequency higher than the more essential voice frequencies, modifying said current by and in accordance with speech, dissipatinga portion of the energy by leaks along'the circuit, reinforcing the modified energy, and passing the arriving energy through a receiver to reproduce speech.

11. The method of transmittingintelligence, which consists in impressing an alternating or fluctuating currentof a frequency higher than the more essential voice frequencies upon a circuit, modifying said current by and maccordance with speech, minimizing distortion of the current-waves by leakage and by inductance, reinforcing the modifiedenergy to overcome the attenuation, and passing the energy through a receiver to reproduce speech.

12. Themethod of transmittingintelligence, which consists in impressing upon a circuit intermediate the transmitting and receiving stations an alternate or fluctuating current, modifying said current in accordance with the message to be transmitted, reinforcing said ourrent by an induction-generator, and passingthe energy through a receiver to reproducea message. 7

13. The method of transmitting intelligence,

which consists in impressing upon a Ci'r'cuitim termediate the transmitting and receiv'ingsta tions an alternating or fluctuating current, modifying said current by and in accordance with the message to be sent, dissipating-a portion of said current by leaks along said circuit, reinforcing said current by an ind uctiongenerator, and passing the cur-rentthrough a receiver to reproducca message.

14:3 The method'of transmittingsimultaneously over a circuit a plurality of. messages; which consists in impressing: UpOn' SMd'CHCuH) aplurality of alternatingorifluctuating currents of different frequencies-modifying each of saidcurrents in accordance with a message to be transmitted, permitting leakage of each of'said currents, reinforcingeach of 'saidcurrents, and selecting each modified current .to a'circuit attuned to its frequency.

15. The method of transmittingsimultaneousl y over a circuit a plurality of independent telephonic messages, which consists in" impress-ing simultaneously upon said circuit a plurality of alternating or fluctuating currents of'different frequencies, the frequency of each current being. higher thanthe more essential frequencies foundin: speech, modifying each alternating or fluctuating current by andin accordance with a spoken message, boosting each current in a circuit selectiveof it, and selecting each current-at a receiving station to acircuit selective of its frequency and including'atelephone-receiver.

16. The method of transmitting simultaneousl y over a circuit aplurality ofindependent telephonic messages,wh1chconsists 1n impres sing upon said circuita plurality of fluctuating currents of different frequencies, the

frequency of each current being higher than the more essential frequencies found in speech, modifying each'current by and in accordance with a spoken message. reducing distortion of said currents by the effects of inductance and leakage, reducing attenuation by reinforcing said currents, and selecting each current toa predeterminedreceiver.

17. The method of reinforcing anelectric ally-transmitted message, which consists in impressing upon a circuit an alternating current of practically constant frequency, varying the amplitudes of the waves in accordance with the message to be sent, reinforcing said alternating current by an induction-generator, and passing. said current through a receiver to reproduce the message.

18. The method of transmitting signals IZC within a wave length, reinforcing said energy, and passing the energy through a receiver to reproduce the signal.

19. The method of transmitting signals which consists in impressing an alternating or fluctuating current upon a circuit, modifyductance, reinforcing said energy, and passing the reinforced energy through a receiver to reproduce the signal.

21. The method of transmitting speech which consists in impressing electric energy upon a circuit, modifying said energy by and in accordance with speech, subjecting said energy to leaks at a plurality of points within a wave length, reinforcing said energy, and passing the reinforced energy through a receiver to reproduce speech.

22. The method of transmitting speech which consists in impressing electrical energy upon a circuit, modifying said energy by and in accordance with speech, reducing distortion of said energy by the efiects of leaks at a plurality of points within a wave length and by the effects of inductance, reinforcing said energy, and passing the reinforced energy through a receiver to reproduce speech.

23. The method of transmitting signals which consists in impressing electric energy upon a circuit, modifying said energy in accordance with a signal to be sent, reducing distortion of said energy by the effects of inductance lumped at a plurality of points within a wave length and by the eflects of leakage, reinforcing said energy, and passing the reinforced energy through a receiver to reproduce the signal.

24. The method of transmitting signals which consists in'impressing electric energy upon a circuit, modifying said energy in accordance with a signal to be sent, reducing distortion of said energy by the efiects of leaks and inductances distributed along the circuit at a plurality of points within a wave length, reinforcing said energy, and passing the reinforced energy through a receiver to reproduce the signal.

25. The method of transmitting signals which consists in impressing an alternating or fluctuating current upon a circuit, modifying said current in accordance with a signal to be sent, reducing the distortion of said current by the effects of inductance lumped at a plurality of points within a wave length and by the effects of leakage, reinforcing said current, and passing the reinforced current through a receiver to reproduce the signal.

26. The method of transmitting signals which consists in impressing an alternating or fluctuating current upon a circuit, modifying said current in accordance with a signal to be sent, reducing distortion of said current by the effects of leaks and inductances distributed along said circuit at a plurality of points within a wave length, reinforcing said current, and passing the reinforced current through a receiver to reproduce the signal.

27. The improvement in the art of transmitting over a circuit electrical energy representing a signal or message, the method which consists in permitting leakage of the transmitted energ, and reinforcing the transmitted energy.

28. The improvement in the art of transmitting over a circuit electrical energy representing a signal or message, the method which consists in reducing distortion of the energy by the effect of leakage, and reinforcing the energy to reduce attenuation.

29. The method of transmitting signals, which consists in impressing upon a circuit an alternating or fluctuating current, modifying said current in accordance with the signal to be sent, and reinforcing said current by an asynchronous alternating-current booster.

30. The method of transmitting signals, which consists in impressing upon a circuit an alternating or fluctuating current, modifying said current in accordance with the signal to be sent, and reinforcing said current by subjecting the primary of an induction-generator to the effects of the transmitted current, and driving the secondary at a speed above synchronism.

31. The method of transmitting speech, which consists in impressing upon a circuit an alternating or fluctuating current, modifying said current by and in accordance with speech, and reinforcing said modified current by subjecting the primary of an induction-generator to the effects of said current, and driving the secondary at a speed above synchronism.

32. The method of transmitting speech, which consists in impressing upon a circuit an alternating or fluctuating current having a frequency high as compared with the more essential frequencies found in speech, modifying said current by and in accordance with speech, and reinforcing said current by subjecting the primary of an induction-generator to the effects of said current, and driving the secondary at a speed above synchronism.

33. The method of transmitting speech, which consists in impressing upon a circuit an alternating or fluctuating current, modifying said current by and in accordance with speech,

IIO

and reinforcing said modified current by an asynchronous alternating-current booster.

34. The method of reinforcing an electrically-transmitted spoken message, which consists in impressing upon a circuit an alternating or fluctuating current of practically constant frequency higher than the more essential frequencies found in speech, varying the amplitudes of the current-Waves by and in ac- IO cordance with speech, reinforcing said our- 

